one of the important cause of pain in knee osteoarthritis

Comparison of the prevalence of myofascial trigger points of muscles
acting on knee between patients with moderate degree of knee
osteoarthritis and healthy matched people

Authors: Amin Kordi Yoosefinejad a, b, Mahbobeh Samani a, *, Fatemeh Jabarifard a,
Mahnaz Setooni a, Rezvan Mirsalari a, Fatemeh Kaviani a,
Seyed Mostafa Jazayeri shooshtaric

a Physical Therapy Department, School of Rehabilitation Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
b Rehabilitation Sciences Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
c Departement of Physical Medicine and Rehabilitation, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

a b s t r a c t

Introduction: Trigger points have been implicated in the development of several musculoskeletal disorders. Trigger points harbored in lower limb muscles might represent a ubiquitous source of pain in patients with knee osteoarthritis (OA). This study was carried out to evaluate the prevalence of Myofascial Trigger Points (MTrPs) in muscles acting on the knee in patients with OA.
Methods: Thirty-seven patients aged at least 55 years old with a moderate degree of OA (grade III of Kellgren and Lawrence scale) were recruited. Thirty asymptomatic people, matched on age and body mass index, were considered as the control group. Ten muscles acting on the knee joint were selected. Taut bands were also identified using a skin rolling method. A pressure of 3 kg/cm2 was used to identify myofascial trigger points in all muscles except the popliteus (8 kg/cm2).
Results: Chi-square was performed to compare the prevalence of trigger points between the groups. The McNemar test was administered to compare the prevalence of trigger points in the right and left sides of participants. Prevalence of the trigger points was significantly higher in patients with knee OA compared with asymptomatic people in all muscles except for right (p = 0.17) and left (p = 0.41) rectus femoris, right (p = 0.61) and left (p = 0.22) sartorius and left biceps femoris (p ¼ 0.08). Comparison of the prevalence of MTrPs bilaterally revealed that only the right and left sartorius differed significantly (p = 0.008).
Conclusions: The prevalence of MTrPs in the muscles acting on the knee joint is higher in patients with a moderate degree of knee OA compared with asymptomatic subjects.

Introduction

Myofascial pain is defined as pain originating from myofascial trigger points (MTrPs) in skeletal muscles (Borg-Stein and Simons, 2002). The term “myofascial pain” was first introduced by Travell and Rinzler (1952). MTrPs are defined as hyperirritable points located within taut bands of the skeletal muscles. They elicit a referral pain with an established predetermined pattern and are considered the major contributors to musculoskeletal pain (Dommerholt et al., 2019; Fern_andez-de-las-Pe~nas and Dommerholt, 2017). MTrPs have been identified in several musculoskeletal disorders such as neck pain syndromes (Han and Harrison, 1997), chronic tension-type headache (Fern_andez-delas- Pe~nas et al., 2006), shoulder impingement and (Bron et al., 2011; Hidalgo-Lozano et al., 2010), and fibromyalgia syndrome (Ge, 2010). The MTrPs are categorized into either active or latent ones. Active MTrPs, upon stimulation/digital pressure, can produce a patient’s familiar pattern or any symptom that is recognized by the patient, including referral, deep pain, dull pain or paresthesia; whereas a latent MTrP, upon stimulation/digital pressure, does not reproduce any symptom experienced previously by the patient, nor are the symptoms that are elicited familiar. Moreover, the presence of spontaneous pain is not always necessary, and many patients represent no symptoms but have active MTrPs (Fern_andez-de-las- Pe~nas and Dommerholt, 2017). Compared with other joints, the knee has a high rate of a predisposition to osteoarthritis (OA) (Heidari, 2011). Recent evidence suggested that OA is a multifactorial entity. It involves multiple causative factors including, inflammation, trauma, mechanical forces, biochemical reactions, and metabolic derangements (Ayhan et al., 2014). Various non-pharmacological interventions such as exercise therapy, electrotherapy, assistive technology, and weight loss are considered beneficial to patients with knee OA (Murphy et al., 2016). Because of the chronic nature of the disease, trigger points harbored in lower extremity muscles may represent a major source of evoked pain in patients with knee OA. Different interventions are proposed to deactivate the trigger points; some of them are as follows: spray and stretch, topical agents, injections, compression therapy, ultrasound, electrotherapy, laser, taping, and dry needling (Gulick, 2016). On the other hand, scant evidence shows the usefulness of surgical interventions in patients with a mild to moderate degree of knee OA (Palmer et al., 2019). Deactivating the trigger points using acupuncture therapy was an efficient method for reducing pain in elderly patients with mild and severe degrees of knee OA (Itoh et al., 2008). Currently, a preliminary study has investigated the association between MTrPs, pain, and function in patients with bilateral knee OA and demonstrated that a greater number of active MTrPs were associated with greater intensity of ongoing pain and reduced physical function (Alburquerque-García et al., 2015); however, the degree of knee joint OA was not determined in this study. Young subjects with anterior knee pain have a greater prevalence of MTrPs in the hip and thigh muscles in comparison to asymptomatic controls, indicating an association between MTrPs and anterior knee pain (Rozenfeld et al., 2019). Similar prevalence and associations were found in patients with secondary OA of the lower limbs and also in patients with total knee arthroplasty (Bajaj et al., 2001;
Henry et al., 2012). The distribution pattern and prevalence of trigger points in patients with a moderate degree of knee OA are yet to be specified. Therefore, the purpose of this study was to determine the prevalence of MTrPs in muscles acting on the knee joint in a homogenous group of patients with a moderate degree of knee OA (grade III of Kellgren and Lawrence scale). We hypothesized that 1. The MTrPs are more prevalent in patients with a moderate degree of knee OA in comparison to asymptomatic matched group and 2. MTrPs are more prevalent in the dominant side of patients compared to the non-dominant side.